When the electrolytic capacitor of a two terminal structure is mounted on a circuit board, the electrolytic capacitor is connected between a power supply line connecting a load circuit such as a CPU (central processing unit) and a power supply circuit supplying DC current to the load circuit, and the ground. Mounting the electrolytic capacitor on the circuit board in this way causes the electrolytic capacitor to function as a secondary battery to supply electrical charges to the load circuit if load fluctuations are generated in the load circuit, while causing the electrolytic capacitor to function as a noise filter to remove high-frequency noise from the power supply line if the high-frequency noise is generated in response to drive of the load circuit.
Recent years have experienced increase of the operating speed of a load circuit and increase of the complexity of the circuit. So, the band of high-frequency noise is shifted to a higher frequency and is broadened. As a result, it becomes difficult for an electrolytic capacitor of a two terminal structure to remove high-frequency noise efficiently.
In response, use of an electrolytic capacitor of a three terminal structure having a low equivalent series inductance (ESL) in place of an electrolytic capacitor of a two terminal structure has been suggested. As an example, patent literature 1 suggests an electrolytic capacitor formed by placing an anode foil and a cathode foil one above the other to which a pair of anode terminals and a cathode terminal are electrically connected respectively, and by winding the anode and cathode foils. In this electrolytic capacitor, a dielectric layer is formed on a surface of the anode foil, and a separator saturated with an electrolytic solution is placed between the dielectric layer and the cathode foil.
When the electrolytic capacitor of a three terminal structure disclosed in patent literature 1 is mounted on a circuit board, the anode terminals as a pair of the electrolytic capacitor are connected to a load circuit and a power supply circuit respectively, and the cathode terminal is connected to the ground. Thus, DC current from the power supply circuit passes through the anode foils of the electrolytic capacitor, and is then supplied to the load circuit. High-frequency noise generated in the load circuit passes through the electrolytic capacitor internally, and is then guided to the ground efficiently.    Patent literature 1: Japanese Patent Application Laid-Open No. 2000-114111